"The presence of several foreign and indigenous terrorist groups poses a potential danger to U.S. citizens throughout Pakistan," the travel warning said.

Those who choose to remain in Pakistan are advised to pay attention to their surroundings, bypass hotels that lack stringent security measures, avoid locations where Westerners are known to congregate and steer clear of crowds.

"Protests against the United States are not uncommon and have the potential to turn violent. U.S. citizens in Pakistan are strongly advised to avoid all protests and large gatherings," the warning stated.

A previous travel warning from September 2012 reminded Americans to be aware of "ongoing security concerns in Pakistan" and urged U.S. citizens to defer all non-essential travel to the country.